Migrating corrosion inhibitor blend for reinforced concrete:: Part 2 -: Inhibitor as repair strategy

The efficiency of a migrating corrosion inhibitor in stopping or reducing corrosion of steel has been investigated in saturated (sat.) calcium hydroxide (Ca[OH](2)) solutions and mortar. In solution, a slight decrease of the corrosion rate was found when the inhibitor blend (10%) was added after the onset of pitting corrosion. Investigation of the diffusion rate in mortar demonstrated the high mobility of the hydroxyalkylamine molecule in porous cement paste. Thus, it was assumed that it is, in principle, possible to obtain high inhibitor concentrations, at the rebar to influence corrosion rate. However, on reinforced mortar samples showing chloride-induced pitting corrosion, no reduction of the corrosion rate could be detected after inhibitor application. The discrepancy between the observed high diffusion rate and the lack of corrosion mitigation was rationalized by the fact that only the diffusion of the volatile component of the inhibitor was measured. Migration of the nonvolatile component (carbonic acids) through concrete was not proved, and it was assumed to have a low diffusion rate. It was concluded that one of the inhibiting constituents of the inhibitor did not reach the rebar, which may explain the lack of inhibiting properties.